Screening of wild deer populations for exposure to SARS‐CoV‐2 in the United Kingdom, 2020–2021

Abstract Following findings in Northern America of SARS‐CoV‐2 infections in white‐tailed deer, there is concern of similar infections in European deer and their potential as reservoirs of SARS‐CoV‐2 including opportunities for the emergence of new variants. UK deer sera were collected in 2020–2021 from 6 species and a hybrid with 1748 tested using anti‐spike and anti‐nucleocapsid serology assays. No samples were positive on both assays nor by surrogate neutralization testing. There is no evidence that spill‐over infections of SARS‐CoV‐2 occurred from the human population to UK deer or that SARS‐CoV‐2 has been circulating in UK deer (over the study period). Although it cannot be ruled out, study results indicate that spill‐over infections followed by circulation of SARS‐CoV‐2 to the most common European deer species is small.


INTRODUCTION
Evidence from Northern America shows the potential of white-tailed deer (WTD, Odocoileus virginianus) as a SARS-CoV-2 reservoir. WTD fawns inoculated with SARS-CoV-2 have been shown to shed infectious virus up to 5 days post-infection. This shedding has been shown to be transmissible to unchallenged contact deer, resulting in seroconversion and the development of neutralizing antibodies Palmer et al., 2021). In addition, SARS-CoV-2 RNA was detected in 36% of free-ranging WTD collected from multiple locations within the state of Ohio during January-March 2021, including evidence of sustained transmission within this deer population (Hale et al., 2021). Furthermore, three different SARS-CoV-2 lineages genetically similar to human viruses were detected indicating that multiple This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. © 2022 Crown copyright. Transboundary and Emerging Diseases published by Wiley-VCH GmbH. This article is published with the permission of the Controller of HMSO and the Queen's Printer for Scotland. reverse zoonosis events are likely to have occurred (Hale et al., 2021). SARS-CoV-2 RNA was also detected in WTD surveyed in Québec, Canada, albeit a lower proportion, with 1.2% of nasal swabs positive (Kotwa et al., 2022). Wider scale exposure in free-ranging WTD across other areas in the United States has also been observed. For example two serosurveillance studies in 2021 of 385 samples collected in Texas (Chandler et al., 2021) and 54 samples collected from Michigan, Pennsylvania, Illinois, New Jersey and New York (Palermo et al., 2021), identified similar seroprevalences of 40% and 37% respectively. Both studies detected neutralizing antibodies based on a surrogate virus neutralization test (sVNT). Evidence of deer-to-deer transmission was also demonstrated in a captive cervid facility in Texas, where 94.4% of WTD sampled were found to be seropositive by neutralization assay.
Two other facilities sampled as part of the study found no evidence of Transbound Emerg Dis. 2022;1-6.
wileyonlinelibrary.com/journal/tbed exposure (Roundy et al., 2022). Informed by these findings, the World Scientists at the UK Health Security Agency (UKHSA) have been using the UK deer population as sentinels for disease surveillance for several years, identifying the emergence of tick-borne encephalitis virus in the United Kingdom via this route in 2019 (Holding et al., 2020). For SARS-CoV-2 three potential outcomes could result from a serosurveillance study in deer: (i) deer are not exposed and therefore no antibody response is detected; (ii) exposure which results in production of an antibody response, but there is no or only lowlevel transmission between deer; or (iii) exposure, onward transmission and established circulation of SARS-CoV-2 within the deer population.

MATERIALS AND METHODS
Deer serum samples were collected by volunteers from routine culling operations in the United Kingdom between January 2020 and May 2021 previously as described (Holding et al., 2020). Blood was sampled from pooled blood within the chest cavity during gralloching; samples were taken as soon as possible after the deer were culled. Ethical approval was granted for the collection of these samples by the Public  (14.8%), Perth and Kinross (8.1%) and Cumbria (6.4%) (Figure 2). The reactivity in the N assay was negligibly low, between 0% and 0.7% for all deer species (Table 1).

DISCUSSION
Results from this study indicate there is no serological evidence of significant circulation of SARS-CoV-2 in UK deer over the study period and provide no evidence that the deer were exposed to SARS-CoV-2.
There was no agreement between the S and N antigen assay results and no neutralizing antibodies to SARS-CoV-2 were detected. Furthermore, there was no evidence of a bimodal distribution, with either the S or N Elecsys® Anti-SARS-CoV-2 assays, which would have been expected for a seropositive subpopulation in a serosurvey (Jacobson, 1998).
Our study findings provide a different picture to that found in WTD across Northern America, where two studies in different loca-tions found high seroprevalences of 40% and 37%; each using the same sVNT as used in this study for confirmatory testing (Chandler et al., 2021;Palermo et al., 2021). While the deer in this study are of different species to the Northern American WTD, it is still possible that UK deer are permissive to SARS-CoV-2, since the angiotensinconverting enzyme 2 (ACE2) receptor is present in all species of deer, though they may have varying sequence differences for the key residues for SARS-CoV-2 binding (Damas et al., 2020). This study suggests that currently, common wild European deer species are not supporting SARS-CoV-2 infections. The low levels of seroreactivity detected by the S and N antigen assays from red and roe deer samples in this study may suggest cross-reactivity with related coronaviruses. Indeed a wide range of coronaviruses are known to circulate in wildlife, livestock and companion animals (Ghai et al., 2021).  (Vijgen et al., 2005(Vijgen et al., , 2006. Many animal coronaviruses cause long-term or persistent enzootic infections. Long periods of coronavirus infection combined with a high mutation rates increase the probability that a virus mutant with an extended host range may arise. Furthermore, given the promiscuous re-combinatory ability of the coronaviruses, which are already known to contribute to their high zoonotic and pandemic potential (Forni et al., 2020;Pratelli et al., 2021), continued monitoring of the UK deer population, including other animal species (Forni et al., 2020;Maurin et al., 2021) would be sensible.